回火处理对多道Ni基熔覆涂层组织和耐蚀性能的影响

Influence of tempering on microstructure and corrosion resistance of multi-pass Ni-based coatings on 45 steel prepared by laser cladding

利用6 kW多模横流CO2激光器在45钢表面熔覆了Ni60CuMoW合金粉末,并对熔覆涂层进行了回火处理。通过OM、XRD、SEM、EDS和电化学综合测试系统等手段分析了激光功率和回火复合处理对熔覆层组织和耐蚀性能的影响。结果表明:熔覆层与基体呈良好的冶金结合,熔覆层组织致密。熔覆层主要由富含Ni的基体相γ(Ni,Fe)、固溶体(Ni,Cu)、化合物Ni31Si12、BCr、Cr5 B3、BNi3、FeNi3和M23 C6(M=Cr、Ni、Fe)等组成。随着激光功率的增加,熔覆层与基体间的过渡区域更加平滑。试样耐蚀性随激光功率的降低而增强,腐蚀电位明显正移,腐蚀电流密度降低近2个数量级。对单道涂层试样,回火处理后的耐蚀性好于回火前,而多道熔覆层的耐腐蚀性又优于单道。

Ni60CuMoW alloy coatings were clad on 45 steel substrate by laser cladding using a 6 kW transverse-flow CO2 laser and the samples were then tempered at 600 ℃.The effects of laser power and tempering treatment on microstructure and corrosion resistance of the clad layer were analyzed by optical microscopy（OM）,X-ray diffraction（XRD）,scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS） and electrochemical tests.The results show that the cladding layer exhibits dense microstructure and metallurgical bonding is obtained between the coating and substrate.The clad coatings are composed of Ni-rich matrix phase γ（Ni,Fe）,solid solution of Ni and Cu,Ni31Si12,Cr5B3,BCr,BNi3 and M23C6（M=Cr、Ni、Fe）.With the increase of laser power,the transition region between clad layer and substrate becomes smoother.The corrosion resistance of treated samples increases with the laser power decrease.Compared with the substrate,the corrosion potential is positive shift,and the corrosion current density decreases by nearly two orders of magnitude.For single-pass clad specimens,the corrosion resistance is improved after tempering treatment,and the corrosion resistance of the multi-pass clad coatings is better than that of the single-pass clad coatings.